Peroxides are used in polymer chemistry for a variety of purposes including, for example, reducing the molecular weight of polymers and vulcanizing rubber. One of the problems associated with the use of peroxides is that in their pure form, peroxides tend to be relatively unstable. Peroxides can break down and lose their activity while in storage. Furthermore, the decomposition and instability of peroxides can present storage and use hazards. For these reasons, peroxides are often diluted with at least one other substance, which improves the stability of the peroxide and facilitates handling. Peroxides that have been diluted with another substance are commonly referred to as “supported peroxides” in the industry.
One known method of forming a supported peroxide product is to melt and spray one or more peroxides onto an inorganic support such as clay or calcium carbonate. The molten peroxide becomes absorbed or adsorbed on the inorganic support and solidifies. The resulting supported peroxide product will be a powder that is easier to handle and is less hazardous than a “pure” peroxide product. One of the drawbacks of inorganic supported grade peroxide products is that the peroxide concentration is generally limited to about 40% by weight, which is the maximum that can be absorbed or adsorbed onto the inorganic support.
Another known method of forming a supported peroxide product is to mill one or more peroxides into a rubber composition to form a master batch product. Master batch products of this type are typically sold as slabs or pellets, which are also easily handled and are substantially less hazardous than pure peroxides. Once again, however, the peroxide concentration for rubber supported grade peroxide products is generally limited to a maximum of about 40% by weight.
Yet another known method of forming a supported peroxide product is to blend one or more peroxides into a molten wax, which is then permitted to cool and solidify. The solidified wax can be granulated or pelletized. It is possible to form supported peroxide products in this manner than have peroxide concentrations of 40% to 70% by weight. One of the drawbacks with wax supported grade peroxide products is that the peroxide must be processed at a high enough temperature to melt the wax, typically above 100° C., which can cause the peroxides to decompose and create a hazardous processing environment. It is also difficult to incorporate other ingredients, such as co-agents and anti-scorch agents, into such compositions.
A need exists for a supported peroxide product that contains a relatively high concentration of peroxide, that can be easily handled, and that can be manufactured at relatively low temperatures.